Snowmobiles driven over adverse riding surfaces, such as snow and ice employ traction devices which penetrate the riding surface to improve operating performances. The traction devices include an elongated, substantially cylindrical, rigid stud having either a conical or a wedge-shaped penetrating bit, and a semi-cylindrical penetrating bit having a flat side and a chisel-shaped or cone-shaped tip. The tip of the cone or wedge-shaped bit or the chisel-shaped tip penetrates the riding surface to dispose a length of the stud in the riding surface. The bit is either affixed to the stud or integrally formed with the stud.
Traction studs are usually formed with the long axis perpendicular to the head or T-nut so that the stud is at right angles to the direction of rotation of the track. A washer and a T-nut are commonly used to affix the stud to a track. Some embodiments of the device are constructed in a "push-through" configuration in which a head is integrally formed with the inner end of the stud on the inner side of the track and a threaded nut and a washer mounted on the outer end of the stud on the outside of the track. The T-nut or head and the washer provide a large contact area with the track. The large contact area minimizes damage to the track as forces are exerted on the traction device.
Studs with a conical shaped bit provide ready, deep penetration of a riding surface. However, the cone shape allows riding surface matter to slide around the cone, resulting in a loss of traction for forward travel of the sled and instability in a lateral direction. The deep penetration of the bit and the small tip also causes accelerated wear of the bit. While providing a more durable bit wedge shaped bits do not penetrate as deeply as conical bits and there is a loss of traction due to the shallow penetration.
Studs with a semi-cylindrical bit having a flat side facing the rear of the sled as the track meets the riding surface and a chisel-shaped tip allow deep penetration and improved traction in the forward direction over the conical and wedge shaped bits. However, the opposite side of the bit presents a semi-circular face to the riding surface and allows snow or dirt to slide around the bit with loss of lateral stability, especially from side-slipping while negotiating corners. Alternatively, as shown in U.S. Pat. No. 5,573,316, milled faces are formed to define a converging angle as they tend toward a conical tip of the stud.
A snowmobile track may have several hundred studs installed on it. Generally, the greater number of studs on the track the better the traction. However, the greater the number of studs added to the track, the more weight that is added to the vehicle. Obviously a heavier vehicle cannot go as fast or handle corners as well as a lighter one. Furthermore, at speed, the added rotating mass tends to configure the track into a circular shape which unfavorably loads the bearings thereby increasing wear and horse power requirements. U.S. Pat. No. 5,573,316 describes a stud made, at least in part, from aluminum rather than steel to reduce the overall weight. However, aluminum is less durable and is subject to rapid wear.
Therefore, the need exists for a traction stud having good penetrating characteristics while providing durable use. The need further exists for a traction stud having increased lateral stability. The need also exists for a traction stud with a reduced weight, thereby allowing greater transfer of available power to motive forces, as well as reducing wear on the track assembly.